A Kinetic Framework for the Pyrolysis of Poly(Ether‐Ketone‐Ketone) ( PEKK )

ABSTRACT Research to date on the thermal degradation of poly(ether‐ketone‐ketone) (PEKK) has largely been limited to low temperatures or analysis as part of a composite. Herein, we investigate the pyrolysis kinetics of neat PEKK from 480°C to 1000°C and characterize the degradation by two global rate‐limiting steps. Isothermal thermogravimetric analysis (TGA) and non‐isothermal TGA with in‐line mass spectroscopy were both employed as methods to isolate components of the two‐step reaction by global and single‐species mass loss phenomena, respectively. The isothermal kinetic analysis method was suitable for determining the kinetic triplet of the primary pyrolysis of poly(ether‐ether‐ketone), which pyrolyzes without cross‐linking in inert atmospheres. In PEKK, however, all kinetic analyses performed were found to be heavily influenced by cross‐linking both before and during the initial pyrolysis step. From these findings, we propose a pyrolysis model that considers the effects of cross‐linking and pyrolysis occurring in parallel. Finally, thermogravimetric mass spectroscopy was used to determine that the cross‐linking of PEKK generates no by‐products, and two potential cross‐linking mechanisms were proposed based on this finding. Because these mechanisms are not mutually exclusive, this study concludes that the onset of PEKK must be modeled accounting for a distribution of cross‐linked products.